The invention relates to a drive train for a vehicle with a relatively high power engine and relatively low weight such as a race car.
Such vehicles are basically highly overpowered. Generally, the full power cannot be applied to the wheels during low speed acceleration, that is, torque transmission must be limited since, otherwise, the driven wheels would slip and, thereby, only reduce the amount of forces available for acceleration of the car. Furthermore, such cars have to cover a large speed range and the high-powered engines are highly tuned for certain power and speed ranges so that it is important for the transmission to accurately ratio-match the engine power tuning for good and efficient engine performance. Race car transmissions have generally five gears to cover the full forward vehicle speed range and as a result make it quite impossible to maintain the engines at optimum speed.
Transmissions with split-torque arrangements in which only part of the torque is transmitted through the transmission speed changing structure and/or a torque converter while the other part is directly transmitted to the drive wheels by mechanical gearing, have been in use. Also transmission arrangements of this type in which, instead of a hydraulic torque converter and/or ratio changing structure, an infinitely variable transmission is used, have become known. Since, however, vehicles require the largest torque at the wheels during low speed acceleration, such transmission structures are always set up for torque recirculation through the gear train loop in order to provide the desired torque at the drive wheels with low vehicle and elevated engine speeds. Such gearing is widely used with torque converters in automobile transmissions and with hydrostatic drives for many industrial applications. If used in such an arrangement in direct regeneration, a Constantly Variable Drive (CVD) is in low ratio when the output speed is low and the CVD changes toward speed-up as the output rpm increases. In this case the transmission output speed range is wider than the CVD output speed range but results in relatively high CVD load because of torque recirculation and results in high CVD loading at higher vehicle operating speeds.